define([
        '../Core/BingMapsApi',
        '../Core/buildModuleUrl',
        '../Core/Cartesian2',
        '../Core/Check',
        '../Core/Credit',
        '../Core/defaultValue',
        '../Core/defined',
        '../Core/defineProperties',
        '../Core/DeveloperError',
        '../Core/Event',
        '../Core/Math',
        '../Core/Rectangle',
        '../Core/Resource',
        '../Core/RuntimeError',
        '../Core/TileProviderError',
        '../Core/WebMercatorTilingScheme',
        '../ThirdParty/when',
        './BingMapsStyle',
        './DiscardMissingTileImagePolicy',
        './ImageryProvider'
    ], function(
        BingMapsApi,
        buildModuleUrl,
        Cartesian2,
        Check,
        Credit,
        defaultValue,
        defined,
        defineProperties,
        DeveloperError,
        Event,
        CesiumMath,
        Rectangle,
        Resource,
        RuntimeError,
        TileProviderError,
        WebMercatorTilingScheme,
        when,
        BingMapsStyle,
        DiscardMissingTileImagePolicy,
        ImageryProvider) {
    'use strict';

    /**
     * Provides tiled imagery using the Bing Maps Imagery REST API.
     *
     * @alias BingMapsImageryProvider
     * @constructor
     *
     * @param {Object} options Object with the following properties:
     * @param {Resource|String} options.url The url of the Bing Maps server hosting the imagery.
     * @param {String} [options.key] The Bing Maps key for your application, which can be
     *        created at {@link https://www.bingmapsportal.com/}.
     *        If this parameter is not provided, {@link BingMapsApi.defaultKey} is used.
     *        If {@link BingMapsApi.defaultKey} is undefined as well, a message is
     *        written to the console reminding you that you must create and supply a Bing Maps
     *        key as soon as possible.  Please do not deploy an application that uses
     *        Bing Maps imagery without creating a separate key for your application.
     * @param {String} [options.tileProtocol] The protocol to use when loading tiles, e.g. 'http:' or 'https:'.
     *        By default, tiles are loaded using the same protocol as the page.
     * @param {BingMapsStyle} [options.mapStyle=BingMapsStyle.AERIAL] The type of Bing Maps imagery to load.
     * @param {String} [options.culture=''] The culture to use when requesting Bing Maps imagery. Not
     *        all cultures are supported. See {@link http://msdn.microsoft.com/en-us/library/hh441729.aspx}
     *        for information on the supported cultures.
     * @param {Ellipsoid} [options.ellipsoid] The ellipsoid.  If not specified, the WGS84 ellipsoid is used.
     * @param {TileDiscardPolicy} [options.tileDiscardPolicy] The policy that determines if a tile
     *        is invalid and should be discarded.  If this value is not specified, a default
     *        {@link DiscardMissingTileImagePolicy} is used which requests
     *        tile 0,0 at the maximum tile level and checks pixels (0,0), (120,140), (130,160),
     *        (200,50), and (200,200).  If all of these pixels are transparent, the discard check is
     *        disabled and no tiles are discarded.  If any of them have a non-transparent color, any
     *        tile that has the same values in these pixel locations is discarded.  The end result of
     *        these defaults should be correct tile discarding for a standard Bing Maps server.  To ensure
     *        that no tiles are discarded, construct and pass a {@link NeverTileDiscardPolicy} for this
     *        parameter.
     *
     * @see ArcGisMapServerImageryProvider
     * @see GoogleEarthEnterpriseMapsProvider
     * @see createOpenStreetMapImageryProvider
     * @see SingleTileImageryProvider
     * @see createTileMapServiceImageryProvider
     * @see WebMapServiceImageryProvider
     * @see WebMapTileServiceImageryProvider
     * @see UrlTemplateImageryProvider
     *
     *
     * @example
     * var bing = new Cesium.BingMapsImageryProvider({
     *     url : 'https://dev.virtualearth.net',
     *     key : 'get-yours-at-https://www.bingmapsportal.com/',
     *     mapStyle : Cesium.BingMapsStyle.AERIAL
     * });
     *
     * @see {@link http://msdn.microsoft.com/en-us/library/ff701713.aspx|Bing Maps REST Services}
     * @see {@link http://www.w3.org/TR/cors/|Cross-Origin Resource Sharing}
     */
    function BingMapsImageryProvider(options) {
        options = defaultValue(options, {});

        //>>includeStart('debug', pragmas.debug);
        if (!defined(options.url)) {
            throw new DeveloperError('options.url is required.');
        }
        //>>includeEnd('debug');

        this._key = BingMapsApi.getKey(options.key);
        this._resource = Resource.createIfNeeded(options.url);
        this._tileProtocol = options.tileProtocol;
        this._mapStyle = defaultValue(options.mapStyle, BingMapsStyle.AERIAL);
        this._culture = defaultValue(options.culture, '');
        this._tileDiscardPolicy = options.tileDiscardPolicy;
        this._proxy = options.proxy;
        this._credit = new Credit('<a href="http://www.bing.com"><img src="' + BingMapsImageryProvider.logoUrl + '" title="Bing Imagery"/></a>');

        /**
         * The default {@link ImageryLayer#gamma} to use for imagery layers created for this provider.
         * Changing this value after creating an {@link ImageryLayer} for this provider will have
         * no effect.  Instead, set the layer's {@link ImageryLayer#gamma} property.
         *
         * @type {Number}
         * @default 1.0
         */
        this.defaultGamma = 1.0;

        this._tilingScheme = new WebMercatorTilingScheme({
            numberOfLevelZeroTilesX : 2,
            numberOfLevelZeroTilesY : 2,
            ellipsoid : options.ellipsoid
        });

        this._tileWidth = undefined;
        this._tileHeight = undefined;
        this._maximumLevel = undefined;
        this._imageUrlTemplate = undefined;
        this._imageUrlSubdomains = undefined;

        this._errorEvent = new Event();

        this._ready = false;
        this._readyPromise = when.defer();

        var metadataResource = this._resource.getDerivedResource({
            url:'/REST/v1/Imagery/Metadata/' + this._mapStyle,
            queryParameters: {
                incl: 'ImageryProviders',
                key: this._key
            }
        });
        var that = this;
        var metadataError;

        function metadataSuccess(data) {
            if (data.resourceSets.length !== 1) {
                metadataFailure();
                return;
            }
            var resource = data.resourceSets[0].resources[0];

            that._tileWidth = resource.imageWidth;
            that._tileHeight = resource.imageHeight;
            that._maximumLevel = resource.zoomMax - 1;
            that._imageUrlSubdomains = resource.imageUrlSubdomains;
            that._imageUrlTemplate = resource.imageUrl;

            var tileProtocol = that._tileProtocol;
            if (!defined(tileProtocol)) {
                // use the document's protocol, unless it's not http or https
                var documentProtocol = document.location.protocol;
                tileProtocol = /^http/.test(documentProtocol) ? documentProtocol : 'http:';
            }

            that._imageUrlTemplate = that._imageUrlTemplate.replace(/^http:/, tileProtocol);

            // Install the default tile discard policy if none has been supplied.
            if (!defined(that._tileDiscardPolicy)) {
                that._tileDiscardPolicy = new DiscardMissingTileImagePolicy({
                    missingImageUrl : buildImageResource(that, 0, 0, that._maximumLevel).url,
                    pixelsToCheck : [new Cartesian2(0, 0), new Cartesian2(120, 140), new Cartesian2(130, 160), new Cartesian2(200, 50), new Cartesian2(200, 200)],
                    disableCheckIfAllPixelsAreTransparent : true
                });
            }

            var attributionList = that._attributionList = resource.imageryProviders;
            if (!attributionList) {
                attributionList = that._attributionList = [];
            }

            for (var attributionIndex = 0, attributionLength = attributionList.length; attributionIndex < attributionLength; ++attributionIndex) {
                var attribution = attributionList[attributionIndex];

                attribution.credit = new Credit(attribution.attribution);

                var coverageAreas = attribution.coverageAreas;

                for (var areaIndex = 0, areaLength = attribution.coverageAreas.length; areaIndex < areaLength; ++areaIndex) {
                    var area = coverageAreas[areaIndex];
                    var bbox = area.bbox;
                    area.bbox = new Rectangle(
                            CesiumMath.toRadians(bbox[1]),
                            CesiumMath.toRadians(bbox[0]),
                            CesiumMath.toRadians(bbox[3]),
                            CesiumMath.toRadians(bbox[2]));
                }
            }

            that._ready = true;
            that._readyPromise.resolve(true);
            TileProviderError.handleSuccess(metadataError);
        }

        function metadataFailure(e) {
            var message = 'An error occurred while accessing ' + metadataResource.url + '.';
            metadataError = TileProviderError.handleError(metadataError, that, that._errorEvent, message, undefined, undefined, undefined, requestMetadata);
            that._readyPromise.reject(new RuntimeError(message));
        }

        function requestMetadata() {
            var metadata = metadataResource.fetchJsonp('jsonp');
            when(metadata, metadataSuccess, metadataFailure);
        }

        requestMetadata();
    }

    defineProperties(BingMapsImageryProvider.prototype, {
        /**
         * Gets the name of the BingMaps server url hosting the imagery.
         * @memberof BingMapsImageryProvider.prototype
         * @type {String}
         * @readonly
         */
        url : {
            get : function() {
                return this._resource.url;
            }
        },

        /**
         * Gets the proxy used by this provider.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Proxy}
         * @readonly
         */
        proxy : {
            get : function() {
                return this._resource.proxy;
            }
        },

        /**
         * Gets the Bing Maps key.
         * @memberof BingMapsImageryProvider.prototype
         * @type {String}
         * @readonly
         */
        key : {
            get : function() {
                return this._key;
            }
        },

        /**
         * Gets the type of Bing Maps imagery to load.
         * @memberof BingMapsImageryProvider.prototype
         * @type {BingMapsStyle}
         * @readonly
         */
        mapStyle : {
            get : function() {
                return this._mapStyle;
            }
        },

        /**
         * The culture to use when requesting Bing Maps imagery. Not
         * all cultures are supported. See {@link http://msdn.microsoft.com/en-us/library/hh441729.aspx}
         * for information on the supported cultures.
         * @memberof BingMapsImageryProvider.prototype
         * @type {String}
         * @readonly
         */
        culture : {
            get : function() {
                return this._culture;
            }
        },

        /**
         * Gets the width of each tile, in pixels. This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Number}
         * @readonly
         */
        tileWidth : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('tileWidth must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._tileWidth;
            }
        },

        /**
         * Gets the height of each tile, in pixels.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Number}
         * @readonly
         */
        tileHeight: {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('tileHeight must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._tileHeight;
            }
        },

        /**
         * Gets the maximum level-of-detail that can be requested.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Number}
         * @readonly
         */
        maximumLevel : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('maximumLevel must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._maximumLevel;
            }
        },

        /**
         * Gets the minimum level-of-detail that can be requested.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Number}
         * @readonly
         */
        minimumLevel : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('minimumLevel must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return 0;
            }
        },

        /**
         * Gets the tiling scheme used by this provider.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {TilingScheme}
         * @readonly
         */
        tilingScheme : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('tilingScheme must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._tilingScheme;
            }
        },

        /**
         * Gets the rectangle, in radians, of the imagery provided by this instance.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Rectangle}
         * @readonly
         */
        rectangle : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('rectangle must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._tilingScheme.rectangle;
            }
        },

        /**
         * Gets the tile discard policy.  If not undefined, the discard policy is responsible
         * for filtering out "missing" tiles via its shouldDiscardImage function.  If this function
         * returns undefined, no tiles are filtered.  This function should
         * not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {TileDiscardPolicy}
         * @readonly
         */
        tileDiscardPolicy : {
            get : function() {
                //>>includeStart('debug', pragmas.debug);
                if (!this._ready) {
                    throw new DeveloperError('tileDiscardPolicy must not be called before the imagery provider is ready.');
                }
                //>>includeEnd('debug');

                return this._tileDiscardPolicy;
            }
        },

        /**
         * Gets an event that is raised when the imagery provider encounters an asynchronous error.  By subscribing
         * to the event, you will be notified of the error and can potentially recover from it.  Event listeners
         * are passed an instance of {@link TileProviderError}.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Event}
         * @readonly
         */
        errorEvent : {
            get : function() {
                return this._errorEvent;
            }
        },

        /**
         * Gets a value indicating whether or not the provider is ready for use.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Boolean}
         * @readonly
         */
        ready : {
            get : function() {
                return this._ready;
            }
        },

        /**
         * Gets a promise that resolves to true when the provider is ready for use.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Promise.<Boolean>}
         * @readonly
         */
        readyPromise : {
            get : function() {
                return this._readyPromise.promise;
            }
        },

        /**
         * Gets the credit to display when this imagery provider is active.  Typically this is used to credit
         * the source of the imagery.  This function should not be called before {@link BingMapsImageryProvider#ready} returns true.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Credit}
         * @readonly
         */
        credit : {
            get : function() {
                return this._credit;
            }
        },

        /**
         * Gets a value indicating whether or not the images provided by this imagery provider
         * include an alpha channel.  If this property is false, an alpha channel, if present, will
         * be ignored.  If this property is true, any images without an alpha channel will be treated
         * as if their alpha is 1.0 everywhere.  Setting this property to false reduces memory usage
         * and texture upload time.
         * @memberof BingMapsImageryProvider.prototype
         * @type {Boolean}
         * @readonly
         */
        hasAlphaChannel : {
            get : function() {
                return false;
            }
        }
    });

    var rectangleScratch = new Rectangle();

    /**
     * Gets the credits to be displayed when a given tile is displayed.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level;
     * @returns {Credit[]} The credits to be displayed when the tile is displayed.
     *
     * @exception {DeveloperError} <code>getTileCredits</code> must not be called before the imagery provider is ready.
     */
    BingMapsImageryProvider.prototype.getTileCredits = function(x, y, level) {
        //>>includeStart('debug', pragmas.debug);
        if (!this._ready) {
            throw new DeveloperError('getTileCredits must not be called before the imagery provider is ready.');
        }
        //>>includeEnd('debug');

        var rectangle = this._tilingScheme.tileXYToRectangle(x, y, level, rectangleScratch);
        var result = getRectangleAttribution(this._attributionList, level, rectangle);

        return result;
    };

    /**
     * Requests the image for a given tile.  This function should
     * not be called before {@link BingMapsImageryProvider#ready} returns true.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level.
     * @param {Request} [request] The request object. Intended for internal use only.
     * @returns {Promise.<Image|Canvas>|undefined} A promise for the image that will resolve when the image is available, or
     *          undefined if there are too many active requests to the server, and the request
     *          should be retried later.  The resolved image may be either an
     *          Image or a Canvas DOM object.
     *
     * @exception {DeveloperError} <code>requestImage</code> must not be called before the imagery provider is ready.
     */
    BingMapsImageryProvider.prototype.requestImage = function(x, y, level, request) {
        //>>includeStart('debug', pragmas.debug);
        if (!this._ready) {
            throw new DeveloperError('requestImage must not be called before the imagery provider is ready.');
        }
        //>>includeEnd('debug');

        return ImageryProvider.loadImage(this, buildImageResource(this, x, y, level, request));
    };

    /**
     * Picking features is not currently supported by this imagery provider, so this function simply returns
     * undefined.
     *
     * @param {Number} x The tile X coordinate.
     * @param {Number} y The tile Y coordinate.
     * @param {Number} level The tile level.
     * @param {Number} longitude The longitude at which to pick features.
     * @param {Number} latitude  The latitude at which to pick features.
     * @return {Promise.<ImageryLayerFeatureInfo[]>|undefined} A promise for the picked features that will resolve when the asynchronous
     *                   picking completes.  The resolved value is an array of {@link ImageryLayerFeatureInfo}
     *                   instances.  The array may be empty if no features are found at the given location.
     *                   It may also be undefined if picking is not supported.
     */
    BingMapsImageryProvider.prototype.pickFeatures = function(x, y, level, longitude, latitude) {
        return undefined;
    };

    /**
     * Converts a tiles (x, y, level) position into a quadkey used to request an image
     * from a Bing Maps server.
     *
     * @param {Number} x The tile's x coordinate.
     * @param {Number} y The tile's y coordinate.
     * @param {Number} level The tile's zoom level.
     *
     * @see {@link http://msdn.microsoft.com/en-us/library/bb259689.aspx|Bing Maps Tile System}
     * @see BingMapsImageryProvider#quadKeyToTileXY
     */
    BingMapsImageryProvider.tileXYToQuadKey = function(x, y, level) {
        var quadkey = '';
        for ( var i = level; i >= 0; --i) {
            var bitmask = 1 << i;
            var digit = 0;

            if ((x & bitmask) !== 0) {
                digit |= 1;
            }

            if ((y & bitmask) !== 0) {
                digit |= 2;
            }

            quadkey += digit;
        }
        return quadkey;
    };

    /**
     * Converts a tile's quadkey used to request an image from a Bing Maps server into the
     * (x, y, level) position.
     *
     * @param {String} quadkey The tile's quad key
     *
     * @see {@link http://msdn.microsoft.com/en-us/library/bb259689.aspx|Bing Maps Tile System}
     * @see BingMapsImageryProvider#tileXYToQuadKey
     */
    BingMapsImageryProvider.quadKeyToTileXY = function(quadkey) {
        var x = 0;
        var y = 0;
        var level = quadkey.length - 1;
        for ( var i = level; i >= 0; --i) {
            var bitmask = 1 << i;
            var digit = +quadkey[level - i];

            if ((digit & 1) !== 0) {
                x |= bitmask;
            }

            if ((digit & 2) !== 0) {
                y |= bitmask;
            }
        }
        return {
            x : x,
            y : y,
            level : level
        };
    };

    BingMapsImageryProvider._logoUrl = undefined;

    defineProperties(BingMapsImageryProvider, {
        /**
         * Gets or sets the URL to the Bing logo for display in the credit.
         * @memberof BingMapsImageryProvider
         * @type {String}
         */
        logoUrl: {
            get: function() {
                if (!defined(BingMapsImageryProvider._logoUrl)) {
                    BingMapsImageryProvider._logoUrl = buildModuleUrl('Assets/Images/bing_maps_credit.png');
                }
                return BingMapsImageryProvider._logoUrl;
            },
            set: function(value) {
                //>>includeStart('debug', pragmas.debug);
                Check.defined('value', value);
                //>>includeEnd('debug');

                BingMapsImageryProvider._logoUrl = value;
            }
        }
    });

    function buildImageResource(imageryProvider, x, y, level, request) {
        var imageUrl = imageryProvider._imageUrlTemplate;

        var subdomains = imageryProvider._imageUrlSubdomains;
        var subdomainIndex = (x + y + level) % subdomains.length;

        return imageryProvider._resource.getDerivedResource({
            url: imageUrl,
            request: request,
            templateValues: {
                quadkey: BingMapsImageryProvider.tileXYToQuadKey(x, y, level),
                subdomain: subdomains[subdomainIndex],
                culture: imageryProvider._culture
            }
        });
    }

    var intersectionScratch = new Rectangle();

    function getRectangleAttribution(attributionList, level, rectangle) {
        // Bing levels start at 1, while ours start at 0.
        ++level;

        var result = [];

        for (var attributionIndex = 0, attributionLength = attributionList.length; attributionIndex < attributionLength; ++attributionIndex) {
            var attribution = attributionList[attributionIndex];
            var coverageAreas = attribution.coverageAreas;

            var included = false;

            for (var areaIndex = 0, areaLength = attribution.coverageAreas.length; !included && areaIndex < areaLength; ++areaIndex) {
                var area = coverageAreas[areaIndex];
                if (level >= area.zoomMin && level <= area.zoomMax) {
                    var intersection = Rectangle.intersection(rectangle, area.bbox, intersectionScratch);
                    if (defined(intersection)) {
                        included = true;
                    }
                }
            }

            if (included) {
                result.push(attribution.credit);
            }
        }

        return result;
    }

    return BingMapsImageryProvider;
});
